In complex computer systems such as those deployed in many business enterprises, security is an obvious concern. Factors requiring serious consideration in connection with the security environment include mobility, the geographic and physical architecture of the system, and the multi-user nature of the systems. In light of the many factors, tokens have become an acceptable way to ensure that users can connect to the system from any convenient work station, even a home-based or remote Internet based terminal in a secure manner.
In computer network environments, security systems based on PKI are gaining popularity as a way of providing security or enhancing existing security, particularly with regard to security for network connections. Generally speaking, a PKI is an arrangement of servers, clients, and specific information that passes between them, for the verification of user identities by one or more trusted third parties such as, for example, one or more Certification Authorities (CA). The specific information is referred to as a public key and is typically associated with or bound to a particular user or users.
The establishment of a public key is typically accomplished by security or PKI software executing at a central location, such as a server, and operating in a coordinated or sometimes uncoordinated fashion with software at client locations. The public keys are typically provided within security certificates specified under, for example, the PKI Working Group (PKIX) of the Internet Engineering Task Force (IETF), which implement certificate standards based on the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation X.509 ITU-T Recommendation X.509 (1997 E): Information Technology—Open Systems Interconnection—The Directory: Authentication Framework, June 1997 also specified in Comité Consultatif International Téléphonique et Télégraphique (CCITT), Geneva, 1989, Data Communication Networks: Directory, Recommendation X.500-X.521, Blue Book, Volume VIII-Fascicle VIII.8 and International Standards Organization/International Engineering Consortium (ISO/IEC), 25 Dec. 1991, Information Technology—Open Systems Interconnection—The Directory: Authentication Framework, ISO/IEC 9594-8 (CCITT Recommendation X.509). The PKIX further specifies additional aspects in connection with request for comments (RFC) 3280, Housley, R., et al., “Internet X.509 Public Key Infrastructure: Certificate and Certificate Revocation List (CRL) Profile”, RFC 3280, April 2002 (supersedes RFC 2459).
Using a PKI, network communications between, for example, a server and a client can be protected such as with a secure socket layer (SSL) connection between the server and client. Originally, SSL was privately developed as a way to provide a secure connection between an Internet web server and a browser operating on a client and has now been adopted as an open security standard by IETF. To operate in a PKI environment, a server wishing to communicate with a client or other network nodes needs to obtain a certificate for validating its identity to the client or other nodes and for allowing an encryption key to be generated for the establishment of the SSL connection. When the client and server first make a connection, the certificate is received by the client and the issuing CA is compared with a root CA certificate stored locally on the client. If the root CA matches the issuing CA then the certificate can be considered trusted. Otherwise a notification can be provided to the client that additional verification steps should be taken to ensure that the server can be “trusted.”
A typical certificate contains the name of the server or other entity that is being identified, the server's public key, the name of the issuing CA, and other information including validity dates and cryptographic information proving that the certificate is authentic, and the serial number of the certificate. When an owner of a token is issued a certificate, the certificate and information associated with the certificate are typically stored in a data structure in a memory area of the token. The information generally would include a public key and a private key identifier or the like that would enable the derivation of a private key allowing content encrypted using the private key to be decrypted. In a scenario, for example, where a token owner wishes to connect to a computer system from a client, the token owner can insert the token into a token interface, and, after entering a password or other means of authentication can connect to a system server. If the user wishes to view an encrypted object, such as an email message of which the user is a recipient, the system can search for the private key in order to decrypt the content as specified for example in connection with the secure multi-purpose mail extension (S/MIME) specification as outlined in RFC 2311, “S/MIME Version 2 Message Specification” Dusse, et al., March 1998 or variants thereof. In practice, the private keys associated with S/MIME can be arbitrarily long and in addition a two-step procedure is generally required to access the private key stored in the token. For example, the server can look at the certificate to obtain a public key for the recipient and then the public key can be used to index into a data structure or storage structure located on the token to obtain the private key. The private key can then be used to decrypt the message.
In a typical security scenario, a security token or smart card can be provided with around 5K bytes of storage. Further, a typical private key can be around 128 bytes and a certificate can be around 1K. It will be appreciated that during the course of a user's tenure within a security environment such as an enterprise, certificates will expire, security servers can change, a user's location can change, a user's email address may change, or the like. Any one of the above noted factors may give rise to the user being issued several certificates during a period of time with an enterprise. In order to ensure that any content, such as old emails, encrypted with early certificates are still readable, all private keys must be maintained in the security token if the corresponding content is to be accessed. In conventional implementations, the certificate is generally also stored.
Difficulties arise when even a modestly large number of certificates are required to be stored in a token. Given the above described potential certificate sizes and the potential sizes of the private keys, even the need to store five certificates would exceed the storage capability of a 5K security token. One solution that may first come to mind would be to simply increase token capacity. However, it is understood that as security connections are made to a server, each having token information associated with it, certain server resources, such as operating system kernel memory are consumed. Thus as token sizes are reduced; the number of simultaneous connections that the server can manage can be increased. It will further be appreciated that increasing the size of the security token would undesirably increase the costs associated with token-based security, particularly for large enterprises. Still further, a typical security token is not intended to act as a large capacity storage device for a variety of reasons including security reasons. In other words, in many highly sensitive security applications, it would be undesirable for a user to be able to store and thereby a large amount of sensitive data from a facility, and particularly undesirable to provide a potential storage place for the sensitive data on the security token. It would be desirable therefore to provide an ability to store private key information, such as private key information for multiple certificates, in a manner that would reduce the size of the corresponding security-related objects.
While a background including problems in the art are described hereinabove, with reference to related art or concepts associated with the present invention, the description is not intended to be limiting since the features of the present invention are set forth in the description which follows. Aspects of the present invention not specifically described herein may become obvious after a review of the attendant description, or may be learned by practice of the invention. Accordingly, it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only in nature and are not restrictive of the scope or applicability of the present invention.